re: 401(k)

The 10 years make a big difference as demonstrated by the graph. I think the idea is to encourage people to save early because it gets you to the steep part of the curve sooner creating even greater wealth (for the same retirement age).

That said, 30 years of solid investment provides a good nest egg. Whether it is enough for a comfortable retirement depends on many factors including life expectancy after retirement and what you think a comfortable life style means.